1. Technical Field
The present invention relates to a light source, a projector, and a method of cooling a discharge lamp.
2. Related Art
In order to exploit the full performance of a discharge lamp including a high-pressure mercury lamp used for a projector or the like, it is necessary to keep the temperature of the coolest part of the discharge lamp, generally, the bottom part on the downside in the vertical direction of the discharge lamp higher.
On the other hand, if the temperature of the discharge lamp is too high, the inner wall of the arc tube of the discharge lamp is subjected to a high temperature and crystallized, and thereby, devitrification that transmittance becomes lower due to opacity may occur. Accordingly, it is necessary to suppress the temperature of the hottest part of the discharge lamp, generally, the top part on the upside in the vertical direction of the discharge lamp to a certain extent.
In this regard, a method of properly cooling the discharge lamp by improving a method of flowing a cooling fluid has been disclosed (for example, Patent Document 1 (JP-2011-221482)).
Usually, cooling of the discharge lamp is designed to provide a proper cooling condition under an initial lighting state. However, in response to the lighting time of the discharge lamp, the temperature of the discharge lamp changes due to changes in electrodes and plasma volume. Accordingly, there has been a problem that, with the cooling settings of the initial lighting, proper cooling of the discharge lamp can not be maintained and the life of the discharge lamp is made shorter.